Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $114.83   13.822%   $130.7018   $130.70   $130.70   $130.70  
  Purchase #2 $203.78   10.570%   $225.3195   $225.32   $225.30   $225.30  
  Purchase #3 $167.92   12.250%   $188.4902   $188.49   $188.50   $188.50  
  Purchase #4 $150.44   10.173%   $165.7443   $165.74   $165.75   $165.70  
  Purchase #5 $221.44   6.632%   $236.1259   $236.13   $236.15   $236.10  
  Purchase #6 $50.41   11.618%   $56.2666   $56.27   $56.25   $56.30  
  Purchase #7 $233.49   11.729%   $260.876   $260.88   $260.90   $260.90  
  7 purchase totals = $1,142.31       $1,263.5243   $1,263.53   $1,263.55   $1,263.50